Display apparatus

ABSTRACT

According to an aspect, a display apparatus includes: a first light-transmissive substrate; a second light-transmissive substrate facing the first light-transmissive substrate; a liquid crystal layer sealed between the first light-transmissive substrate and the second light-transmissive substrate, and including polymer dispersed liquid crystal; at least one light-emitting device facing at least one of a side surface of the first light-transmissive substrate or a side surface of the second light-transmissive substrate; and a display controller configured to perform control so as to reduce power consumption based on a signal, the signal being in accordance with a signal of external light intensity information supplied from an external light setting device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Application No.2016-183513, filed on Sep. 20, 2016, the contents of which areincorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a display apparatus.

2. Description of the Related Art

Japanese Patent Application Laid-open Publication No. 2008-242354(JP-A-2008-242354) discloses a display apparatus including lightintensity sensors.

In the self-luminescent display apparatus disclosed in JP-A-2008-242354,background light on a second surface side opposite to a first surfaceside of a display panel is blocked, which make it hard for a backgroundon the second surface side to be visually recognized from the firstsurface of the display panel.

SUMMARY

According to an aspect, a display apparatus includes: a firstlight-transmissive substrate; a second light-transmissive substratefacing the first light-transmissive substrate; a liquid crystal layersealed between the first light-transmissive substrate and the secondlight-transmissive substrate, and including polymer dispersed liquidcrystal; at least one light-emitting device facing at least one of aside surface of the first light-transmissive substrate or a side surfaceof the second light-transmissive substrate; and a display controllerconfigured to perform control so as to reduce power consumption based ona signal, the signal being in accordance with a signal of external lightintensity information supplied from an external light setting device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an example of a displayapparatus according to a configurational embodiment;

FIG. 2 is a block diagram illustrating the display apparatus of FIG. 1;

FIG. 3 is a timing chart for explaining timing to emit light by a lightsource according to a field sequential method;

FIG. 4 is an explanatory diagram illustrating a relation between avoltage applied to a pixel electrode and a scattering state of a pixel;

FIG. 5 is a cross-sectional view illustrating an example of across-section of the display apparatus of FIG. 1;

FIG. 6 is a plan view illustrating a plane of the display apparatus ofFIG. 1;

FIG. 7 is an enlarged cross-sectional view of a liquid crystal layersection of FIG. 5;

FIG. 8 is a cross-sectional view for explaining a non-scattering statein a liquid crystal layer;

FIG. 9 is a cross-sectional view for explaining a scattering state inthe liquid crystal layer;

FIG. 10 is a plan view illustrating a pixel;

FIG. 11 is a cross-sectional view taken along line XI-XI illustrated inFIG. 10;

FIG. 12 is a diagram for explaining incident light from a light-emittingdevice;

FIG. 13 is a diagram for explaining the influence of external light onradiance in a pixel;

FIG. 14 is a diagram for explaining a relation between a distance fromthe light-emitting device to each pixel and radiance in a state in whichno external light is incident on a display panel;

FIG. 15 is a diagram for explaining a relation between a distance fromthe light-emitting device to each pixel and radiance in a state in whichexternal light is incident on the display panel;

FIG. 16 is a diagram for explaining a lower limit value of a pixelvoltage;

FIG. 17 is an explanatory diagram illustrating an example of a colorgradation value of one pixel of an image in accordance with an imageinput signal;

FIG. 18 is an explanatory diagram illustrating an example of a colorgradation value of one pixel of an adjusted image according to theconfigurational embodiment;

FIG. 19 is a plan view illustrating the plane of a display apparatusaccording to a first modification of the configurational embodiment;

FIG. 20 is a cross-sectional view taken along line XX-XX illustrated inFIG. 19;

FIG. 21 is a plan view illustrating the plane of a display apparatusaccording to a second modification of the configurational embodiment;

FIG. 22 is a cross-sectional view taken along line XXII-XXII illustratedin FIG. 21; and

FIG. 23 is a cross-sectional view taken along line XXIII-XXIIIillustrated in FIG. 21.

DETAILED DESCRIPTION

Modes (embodiments) for carrying out the present disclosure will bedescribed in detail with reference to the drawings. The presentdisclosure is not limited by the descriptions of the followingembodiments. The elements described hereunder include those that can beeasily thought of by those skilled in the art and substantially the sameelements. The elements described hereunder may also be combined asappropriate. The disclosure is merely an example, and the presentinvention naturally encompasses appropriate modifications maintainingthe gist of the invention that is easily conceivable by those skilled inthe art. To further clarify the description, a width, a thickness, ashape, and the like of each component may be schematically illustratedin the drawings as compared with an actual aspect. However, this ismerely an example and interpretation of the invention is not limitedthereto. The same elements as those described in the drawings that havealready been discussed are denoted by the same reference numeralsthroughout the description and the drawings, and detailed descriptionthereof will not be repeated in some cases. In this disclosure, when anelement is described as being “on” another element, the element can bedirectly on the other element, or there can be one or more elementsbetween the element and the other element.

FIG. 1 is a perspective view illustrating an example of a displayapparatus according to a configurational embodiment. FIG. 2 is a blockdiagram illustrating the display apparatus of FIG. 1. FIG. 3 is a timingchart for explaining timing to emit light by a light source according toa field sequential method.

As illustrated in FIG. 1, a display apparatus 1 includes: a displaypanel 2; a side light source device 3; a drive circuit 4 thatconstitutes a part of a display controller 5 (see FIG. 2) to bedescribed below; and an external light setting device 61. Here, onedirection of the plane of the display panel 2 is referred to as an Xdirection, a direction that is orthogonal to the X direction is referredto as a Y direction, and a direction that is orthogonal to an X-Y planeis referred to as a Z direction.

The display panel 2 includes a first light-transmissive substrate 10, asecond light-transmissive substrate 20, and a liquid crystal layer 50(see FIG. 5). The second light-transmissive substrate 20 faces the firstlight-transmissive substrate 10 in a direction (the Z directionillustrated in FIG. 1) perpendicular to the surface of the firstlight-transmissive substrate 10. Polymer dispersed liquid crystaldescribed below is sealed in the liquid crystal layer 50 (see FIG. 5)with the first light-transmissive substrate 10, the secondlight-transmissive substrate 20, and a sealant 19.

As illustrated in FIG. 1, the inside of the sealant 19 serves as adisplay area in the display panel 2. In the display area, a plurality ofpixels Pix are arranged in a matrix pattern. In the present disclosure,a row refers to a pixel row having m pixels Pix arranged in a direction,and a column refers to a pixel column having n pixels Pix arranged in adirection perpendicular to the direction in which the rows are arranged.The values of m and n are determined according to a display resolutionin the vertical direction and a display resolution in the horizontaldirection. A plurality of scanning lines 12 are routed in respectiverows and a plurality of signal lines 13 are routed in respectivecolumns.

The side light source device 3 includes a light-emitting device 31. Asillustrated in FIG. 2, a light source controller 32, a light sourcesubstrate 33 in which the light-emitting device 31 and the light sourcecontroller 32 are arranged, and the drive circuit 4 constitute thedisplay controller 5. The light source substrate 33 is a flexiblesubstrate and also functions as wiring for electrically coupling thelight source controller 32 and the drive circuit 4 with each other (seeFIG. 2). The light-emitting device 31 and the light source controller 32are electrically coupled with each other through wiring in the lightsource substrate 33.

For example, the external light setting device 61 is an external lightintensity sensor, which detects the intensity of external light 69 froman external illuminator Q and generates a signal ELV of external lightintensity information according to the intensity of the external light69. The external light setting device 61 transmits the generated signalELV of the external light intensity information to the drive circuit 4.The external light setting device 61 is fixed to the surface of thefirst light-transmissive substrate 10. The external light setting device61 may be fixed at any position as long as it can detect the intensityof the external light 69 on the periphery of the display panel 2.

For example, the external light setting device 61 is not limited to anexternal light intensity sensor, and may be an external light intensitysetting switch. The external light intensity setting switch generatesthe signal ELV of the external light intensity information based on asetting value of the external light intensity information set in advanceaccording to the intensity of the external light 69 by an observer. Forexample, the external light intensity setting switch has predeterminedsetting values of the external light intensity information for each ofenvironmental modes, such as a sunlight clear sky mode (firstenvironment mode), a sunlight cloudy sky mode (second environment mode),an indoor use mode (third environment mode), and a night-time use mode(fourth environment mode). The setting values of the external lightintensity information, for example, are decreased in the order of thesunlight clear sky mode (first environment mode), the sunlight cloudysky mode (second environment mode), the indoor use mode (thirdenvironment mode), and the night-time use mode (fourth environmentmode). Thus, the values of the signals ELV of the external lightintensity information are also decreased in the order of the sunlightclear sky mode (first environment mode), the sunlight cloudy sky mode(second environment mode), the indoor use mode (third environment mode),and the night-time use mode (fourth environment mode). The externallight setting device 61 transmits the generated signal ELV of theexternal light intensity information to the drive circuit 4. In a casewhere the external light setting device 61 is an external lightintensity setting switch, the external light intensity setting switchmay be fixed at any positions as long as it can transmit the signal ELVof the external light intensity information to the drive circuit 4.

As illustrated in FIG. 1, the drive circuit 4 is fixed to the surface ofthe first light-transmissive substrate 10. As illustrated in FIG. 2, thedrive circuit 4 includes an analyzer 41, a pixel controller 42, a gatedriver 43, a source driver 44, and a common potential driver 45. Thearea of the XY plane of the first light-transmissive substrate 10 islarger than that of the second light-transmissive substrate 20, and thedrive circuit 4 is disposed in an exposed portion of the firstlight-transmissive substrate 10 that is exposed from the secondlight-transmissive substrate 20.

An image input signal (e.g., RGB data) VS is input to the analyzer 41from an image output device 91 of an external host controller 9 througha flexible substrate 92.

The analyzer 41 includes an input signal analyzer 411, an external lightanalyzer 412, a storage 413, and a signal adjuster 414. The input signalanalyzer 411 generates an image control signal VCS and a light sourcecontrol signal LCS in accordance with an image input signal VS inputfrom the outside. The light source control signal LCS is, for example, asignal including light amount information of the light-emitting device31 to be set according to an average of input gradation values for allthe pixels Pix. For example, in a case where a dark image is displayed,the light amount of the light-emitting device 31 is set to be small. Onthe other hand, in a case where a bright image is displayed, the lightamount of the light-emitting device 31 is set to be large.

The image control signal VCS is a signal for determining a gradationvalue to be given to each pixel Pix of the display panel 2 in accordancewith the image input signal VS. In other words, the image control signalVCS is a signal including gradation information about a gradation valueof each pixel Pix. The pixel controller 42 sets an output gradationvalue by performing a correction process such as a gamma correctionprocess and an expansion process for an input gradation value of theimage control signal VCS.

The signal ELV of the external light intensity information is input tothe external light analyzer 412 from the external light setting device61 described above. The external light analyzer 412 generates anadjustment signal LAS in accordance with the signal ELV of the externallight intensity information based on a lookup table stored in thestorage 413.

The signal adjuster 414 generates a light source control signal LCSAfrom the light source control signal LCS in accordance with theadjustment signal LAS, and transmits the generated light source controlsignal to the light source controller 32. The signal adjuster 414generates an image control signal VCSA from the image control signal VCSin accordance with the adjustment signal LAS, and transmits thegenerated image control signal to the pixel controller 42.

The pixel controller 42 then generates a horizontal drive signal HDS anda vertical drive signal VDS in accordance with the image control signalVCSA. In the configurational embodiment, driving is performed by thefield sequential method, and thus the horizontal drive signal HDS andthe vertical drive signal VDS are generated for each color that can beemitted by the light-emitting device 31.

The gate driver 43 sequentially selects the scanning lines 12 of thedisplay panel 2 in one vertical scanning period in accordance with thehorizontal drive signal HDS. The order in which the scanning lines 12are selected is arbitrary.

The source driver 44 supplies a gradation signal according to an outputgradation value of each pixel Pix to each signal line 13 of the displaypanel 2 in accordance with the vertical drive signal VDS in onehorizontal scanning period.

In the configurational embodiment, the display panel 2 is an activematrix-type panel. For this reason, the display panel 2 includes thescanning (gate) lines 12 extending in the X direction and the signal(source) lines 13 extending in the Y direction in the plan view, andincludes switching elements Tr at intersections of the scanning lines 12and the signal lines 13.

A thin film transistor is used as the switching element Tr. Examples ofthe thin film transistor include, but are not limited to, a bottomgate-type transistor and a top gate-type transistor. In the description,a single-gate thin film transistor is exemplified as the switchingelement Tr, but a double-gate transistor may be used. One of a sourceelectrode and a drain electrode of the switching element Tr is coupledto the signal line 13, a gate electrode thereof is coupled to thescanning line 12, and the other of the source electrode and the drainelectrode is coupled to one end of capacitance LC of a liquid crystal.The capacitance LC of the liquid crystal has one end coupled to theswitching element Tr through a pixel electrode 16, and the other endcoupled to a common potential COM through a common electrode 22. Thecommon potential COM is supplied from the common potential driver 45.

The light-emitting device 31 includes a luminous body 34R of a firstcolor (for example, red), a luminous body 34G of a second color (forexample, green), and a luminous body 34B of a third color (for example,blue). The light source controller 32 controls the luminous body 34R ofthe first color, the luminous body 34G of the second color, and theluminous body 34B of the third color to emit light in a time divisionmanner, in accordance with the light source control signal LCSA. In thisway, the luminous body 34R of the first color, the luminous body 34G ofthe second color, and the luminous body 34B of the third color aredriven by the so-called field sequential method.

As illustrated in FIG. 3, in a first sub-frame (first predeterminedtime) RON, the luminous body 34R of the first color emits light, and thepixels Pix selected within one vertical scanning period GateScantransmit and display the light. At this time, in the entire displaypanel 2, if the gradation signal according to the output gradation valueof each of the pixels Pix selected within the one vertical scanningperiod GateScan is supplied to each of the above-described signal lines13, only the first color is lighted.

Next, in a second sub-frame (second predetermined time) GON, theluminous body 34G of the second color emits light, and the pixels Pixselected within one vertical scanning period GateScan transmit anddisplay the light. At this time, in the entire display panel 2, if thegradation signal according to the output gradation value of each of thepixels Pix selected within the one vertical scanning period GateScan issupplied to each of the above-described signal lines 13, only the secondcolor is lighted.

Further, in a third sub-frame (third predetermined time) BON, theluminous body 34B of the third color emits light, and the pixels Pixselected within one vertical scanning period GateScan transmit anddisplay the light. At this time, in the entire display panel 2, if thegradation signal according to the output gradation value of each of thepixels Pix selected within the one vertical scanning period GateScan issupplied to each of the above-described signal lines 13, only the thirdcolor is lighted.

The eyes of a human have a limited temporal resolution, and see anafterimage. Thus, the eyes of a human recognize a synthesized image ofthree colors in one frame period. The field sequential method requiresno color filter, and suppresses an absorption loss in color filters,which can realize high transmittance. In a color filter method, onepixel is made of sub-pixels obtained by dividing the pixel into thefirst color, the second color, and the third color. On the other hand,the field sequential method does not require such division intosub-pixels, and thus can facilitate increase of the resolution.

FIG. 4 is an explanatory diagram illustrating a relation between avoltage applied to a pixel electrode and a scattering state of a pixel.FIG. 5 is a cross-sectional view illustrating an example of across-section of the display apparatus of FIG. 1. FIG. 6 is a plan viewillustrating a plane of the display apparatus of FIG. 1. FIG. 5 is across-sectional view taken along line V-V illustrated in FIG. 6. FIG. 7is an enlarged cross-sectional view of a liquid crystal layer section ofFIG. 5. FIG. 8 is a cross-sectional view for explaining a non-scatteringstate in a liquid crystal layer. FIG. 9 is a cross-sectional view forexplaining a scattering state in the liquid crystal layer.

If a gradation signal according to the output gradation value of each ofthe pixels Pix selected within the one vertical scanning period GateScanis supplied to each of the above-described signal lines 13, a voltageapplied to the pixel electrode 16 is changed according to the gradationsignal. If the voltage applied to the pixel electrode 16 is changed, avoltage between the pixel electrode 16 and the common electrode 22 ischanged. Then, as illustrated in FIG. 4, the scattering state of theliquid crystal layer 50 of each pixel Pix is controlled, and thescattering ratio of the pixel Pix is changed, according to the voltageapplied to the pixel electrode 16.

As illustrated in FIGS. 5 and 6, the first light-transmissive substrate10 includes a first principal surface 10A, a second principal surface10B, a first side surface 10C, a second side surface 10D, a third sidesurface 10E, and a fourth side surface 10F. The first principal surface10A and the second principal surface 10B are planes parallel to eachother. The first side surface 10C and the second side surface 10D areplanes parallel to each other. The third side surface 10E and the fourthside surface 10F are planes parallel to each other.

As illustrated in FIGS. 5 and 6, the second light-transmissive substrate20 includes a first principal surface 20A, a second principal surface20B, a first side surface 20C, a second side surface 20D, a third sidesurface 20E, and a fourth side surface 20F. The first principal surface20A and the second principal surface 20B are planes parallel to eachother. The first side surface 20C and the second side surface 20D areplanes parallel to each other. The third side surface 20E and the fourthside surface 20F are planes parallel to each other.

As illustrated in FIGS. 5 and 6, the light-emitting device 31 faces thefirst side surface 20C of the second light-transmissive substrate 20. Asillustrated in FIG. 5, the light-emitting device 31 emits light sourcelight L to the first side surface 20C of the second light-transmissivesubstrate 20. The first side surface 20C, which faces the light-emittingdevice 31, of the second light-transmissive substrate 20 serves as alight incident surface. A gap G is provided between the light-emittingdevice 31 and the light incident surface. The gap G serves as an airlayer.

As illustrated in FIG. 5, the light source light L emitted from thelight-emitting device 31 propagates in a direction away from the firstside surface 20C while being reflected at the first principal surface10A of the first light-transmissive substrate 10 and the first principalsurface 20A of the second light-transmissive substrate 20. When thelight source light L travels from the first principal surface 10A of thefirst light-transmissive substrate 10 or the first principal surface 20Aof the second light-transmissive substrate 20 toward the outside, thelight source light travels from a medium having a high refractive indexto a medium having a low refractive index. Accordingly, if an incidentangle of the light source light L entering the first principal surface10A of the first light-transmissive substrate 10 or the first principalsurface 20A of the second light-transmissive substrate 20 is larger thana critical angle, the light source light L is totally reflected at thefirst principal surface 10A of the first light-transmissive substrate 10or the first principal surface 20A of the second light-transmissivesubstrate 20.

As illustrated in FIG. 5, the light source light L propagating throughthe inside of the first light-transmissive substrate 10 and that of thesecond light-transmissive substrate 20 is scattered in the pixel Pixhaving a liquid crystal in the scattering state, and the incident angleof the scattered light becomes smaller than the critical angle. Radiantlight 68 and radiant light 68A are respectively radiated from the firstprincipal surface 20A of the second light-transmissive substrate 20 andthe first principal surface 10A of the first light-transmissivesubstrate 10 to the outside. The radiant light 68 and the radiant light68A radiating respectively from the first principal surface 20A of thesecond light-transmissive substrate 20 and the first principal surface10A of the first light-transmissive substrate 10 to the outside areobserved by an observer. In the present disclosure, a value representingthe degree of luminance of the radiant light 68 or the radiant light 68Ain the pixel Pix will be referred to as a radiance gradation value. Thefollowing describes polymer dispersed liquid crystal in the scatteringstate and polymer dispersed liquid crystal in the non-scattering statewith reference to FIGS. 7 to 9.

As illustrated in FIG. 7, a first orientation film 55 is arranged in thefirst light-transmissive substrate 10. A second orientation film 56 isarranged in the second light-transmissive substrate 20. The firstorientation film 55 and the second orientation film 56 are, for example,vertical orientation films.

A solution in which liquid crystal is dispersed in monomers is sealedbetween the first light-transmissive substrate 10 and the secondlight-transmissive substrate 20. Next, the monomers are polymerized byultraviolet rays or heat in a state where the monomers and the liquidcrystal are oriented by the first orientation film 55 and the secondorientation film 56 to form a bulk 51. This process forms the liquidcrystal layer 50 including the polymer dispersed liquid crystal in areverse mode in which the liquid crystal is dispersed in gaps of apolymer network formed in a mesh manner.

In this way, the liquid crystal layer 50 includes the bulk 51 formed ofthe polymer, and a plurality of fine particles 52 dispersed in the bulk51. The fine particles 52 are formed of the liquid crystal. The bulk 51and the fine particles 52 each have optical anisotropy.

The orientation of the liquid crystal included in the fine particles 52is controlled based on a voltage difference between the pixel electrode16 and the common electrode 22. The orientation of the liquid crystal ischanged according to a voltage applied to the pixel electrode 16. Thedegree of scattering of the light that passes through the pixel Pix ischanged in accordance with the change of the orientation of the liquidcrystal.

For example, as illustrated in FIG. 8, in a state in which no voltage isapplied between the pixel electrode 16 and the common electrode 22, thedirection of the optical axis Ax1 of the bulk 51 and the direction ofthe optical axis Ax2 of the fine particles 52 are the same. The opticalaxis Ax2 of the fine particles 52 is parallel to the Z direction of theliquid crystal layer 50. The optical axis Ax1 of the bulk 51 is parallelto the Z direction of the liquid crystal layer 50 regardless of whetheror not a voltage is applied thereto.

An ordinary light refractive index of the bulk 51 and that of the fineparticles 52 are equal to each other. In a state in which no voltage isapplied between the pixel electrode 16 and the common electrode 22, adifference in the refractive indexes between the bulk 51 and the fineparticles 52 becomes zero in all directions. The liquid crystal layer 50becomes the non-scattering state in which the liquid crystal layer 50does not scatter the light source light L. The light source light Lpropagates in a direction away from the light-emitting device 31 whilebeing reflected at the first principal surface 10A of the firstlight-transmissive substrate 10 and the first principal surface 20A ofthe second light-transmissive substrate 20. When the liquid crystallayer 50 is in the non-scattering state in which the liquid crystallayer 50 does not scatter the light source light L, a background on thefirst principal surface 20A side of the second light-transmissivesubstrate 20 is visually recognized from the first principal surface 10Aof the first light-transmissive substrate 10, and a background on thefirst principal surface 10A side of the first light-transmissivesubstrate 10 is visually recognized from the first principal surface 20Aof the second light-transmissive substrate 20.

As illustrated in FIG. 9, the optical axis Ax2 of the fine particle 52is inclined by an electric field generated between the pixel electrode16 and the common electrode 22 to which a voltage is applied. Since theoptical axis Ax1 of the bulk 51 remains unchanged by the electric field,the direction of the optical axis Ax1 of the bulk 51 and the directionof the optical axis Ax2 of the fine particles 52 are different from eachother. The light source light L is scattered in the pixel Pix having thepixel electrode 16 to which a voltage is applied. As described above, apart of the scattered light source light L that is radiated from thefirst principal surface 10A of the first light-transmissive substrate 10or the first principal surface 20A of the second light-transmissivesubstrate 20 to the outside is observed by an observer.

In the pixel Pix having the pixel electrode 16 to which no voltage isapplied, the background on the first principal surface 20A side of thesecond light-transmissive substrate 20 is visually recognized from thefirst principal surface 10A of the first light-transmissive substrate10, and the background on the first principal surface 10A side of thefirst light-transmissive substrate 10 is visually recognized from thefirst principal surface 20A of the second light-transmissive substrate20. In the display apparatus 1 according to the configurationalembodiment, when an image input signal VS is input from the image outputdevice 91, a voltage is applied to the pixel electrode 16 of the pixelPix displaying an image, and the image in accordance with the imageinput signal VS is visually recognized together with the background.

The image displayed according to the light source light L scattered andradiated to the outside in the pixel Pix having the pixel electrode 16to which a voltage is applied superimposes the background to bedisplayed. In other words, the display apparatus 1 according to theconfigurational embodiment displays the image superimposing thebackground by combining the radiant light 68 or the radiant light 68Awith the background.

FIG. 10 is a plan view illustrating a pixel. FIG. 11 is across-sectional view taken along line XI-XI illustrated in FIG. 10. Asillustrated in FIGS. 1, 2, and 10, the first light-transmissivesubstrate 10 is provided with the signal lines 13 and the scanning lines12 in a grid manner in plan view. A region surrounded by adjacentscanning lines 12 and adjacent signal lines 13 is the pixel Pix. Thepixel Pix is provided with the pixel electrode 16 and the switchingelement Tr. In the configurational embodiment, the switching element Tris a bottom gate thin film transistor. The switching element Tr includesa semiconductor layer 15 that overlaps a gate electrode 12G electricallycoupled to the scanning line 12 in plan view.

The scanning line 12 is wiring made of a metal such as molybdenum (Mo)and aluminum (Al), a layered body of the aforementioned metal, or analloy of the aforementioned metal. The signal line 13 is wiring made ofa metal such as aluminum, or an alloy.

The semiconductor layer 15 is arranged not to protrude from the gateelectrode 12G in plan view. This configuration causes the light sourcelight L traveling from the gate electrode 12G side toward thesemiconductor layer 15 to be reflected, and is less likely to causeleakage of light in the semiconductor layer 15.

As illustrated in FIG. 10, a source electrode 13S electrically coupledto the signal line 13 overlaps one end portion of the semiconductorlayer 15 in plan view.

As illustrated in FIG. 10, a drain electrode 14D is provided in aposition adjacent to the source electrode 13S across a central portionof the semiconductor layer 15 in plan view. The drain electrode 14Doverlaps the other end portion of the semiconductor layer 15 in planview. A portion of the semiconductor layer 15 not overlapping the sourceelectrode 13S and the drain electrode 14D functions as a channel of theswitching element Tr. As illustrated in FIG. 11, conductive wiring 14coupled to the drain electrode 14D is electrically coupled to the pixelelectrode 16 through a through hole SH.

As illustrated in FIG. 11, the first light-transmissive substrate 10includes a first base member 11 formed of glass, for example. The firstbase member 11 may be a resin such as polyethylene terephthalate as longas the resin has light-transmissive properties. A first insulating layer17 a is provided on the first base member 11, and the scanning line 12and the gate electrode 12G are provided on the first insulating layer 17a. A second insulating layer 17 b is provided to cover the scanning line12. The first insulating layer 17 a and the second insulating layer 17 bare formed of a transparent inorganic insulating member such as siliconnitride.

The semiconductor layer 15 is stacked on the second insulating layer 17b. The semiconductor layer 15 is formed of amorphous silicon. However,the semiconductor layer 15 may be formed of polysilicon or an oxidesemiconductor.

The source electrode 13S that covers a part of the semiconductor layer15, the signal line 13, the drain electrode 14D that covers a part ofthe semiconductor layer 15, and the conductive wiring 14 are provided onthe second insulating layer 17 b. The signal line 13 and the drainelectrode 14D are formed of the same material. A third insulating layer17 c is provided on the semiconductor layer 15, the signal line 13, andthe drain electrode 14D. The third insulating layer 17 c is formed of atransparent inorganic insulating member such as silicon nitride.

The pixel electrode 16 is provided on the third insulating layer 17 c.The pixel electrode 16 is formed of a light-transmissive conductivemember such as indium tin oxide (ITO). The pixel electrode 16 iselectrically coupled to the conductive wiring 14 and the drain electrode14D through a contact hole provided in the third insulating layer 17 c.The first orientation film 55 is provided on the pixel electrode 16.

The second light-transmissive substrate 20 includes a second base member21 formed of glass, for example. The second base member 21 may be aresin such as polyethylene terephthalate as long as the resin haslight-transmissive properties. The common electrode 22 is provided onthe second base member 21. The common electrode 22 is formed of alight-transmissive conductive member such as ITO. The second orientationfilm 56 is provided on the surface of the common electrode 22.

FIG. 12 is a diagram illustrating incident light incident from thelight-emitting device. When light from the light-emitting device 31enters the first side surface 20C of the second light-transmissivesubstrate 20 at an angle θ0, the light enters the first principalsurface 20A of the second light-transmissive substrate 20 at an anglei1. In a case where the angle i1 is larger than the critical angle, thelight source light L totally reflected at the first principal surface20A of the second light-transmissive substrate 20 at an angle i2propagates through the inside of the second light-transmissive substrate20. Since the gap G is formed between the light-emitting device 31 andthe first side surface 20C (light incident surface) illustrated in FIG.12, light source light LN having an angle θN by which the angle i1becomes smaller than the critical angle is not guided to the first sidesurface 20C of the second light-transmissive substrate 20.

First Embodiment

FIG. 13 is a diagram for explaining the influence of external light onradiance in a pixel. As illustrated in FIG. 4, the scattering ratio of apixel Pix increases according to a voltage applied to a pixel electrode.For this reason, as illustrated in FIG. 13, when a voltage applied tothe pixel electrode increases in the order of a voltage V1, a voltageV2, and a voltage V3, a radiance gradation value according to lightsource light increases in the order of the voltage V1, the voltage V2,and the voltage V3 applied to the pixel electrode along a firstcharacteristic graph Tsc. In a state in which no external light isincident on a display panel 2, a gradation value of luminance of thelight source light is the radiance gradation value. The firstcharacteristic graph Tsc indicates that a radiance gradation valueaccording to the light source light when the voltage V3 is applied tothe pixel electrode is “255”, which is the maximum value of the 8-bitgradation. In the state in which no external light is incident on thedisplay panel 2, the first characteristic graph Tsc indicates that theradiance gradation value does not reach “255” when the voltage V1 or thevoltage V2 is applied to the pixel electrode.

As a comparative example, a transmissive liquid crystal panel having anordinary backlight needs to make an image brighter as external lightentering the panel becomes stronger, which requires increase in outputof the backlight. On the other hand, the display apparatus 1 accordingto the configurational embodiment includes no backlight. Thus, in thedisplay apparatus 1 according to the configurational embodiment, whenexternal light is incident on the display panel 2, the external light isscattered in the pixel Pix in accordance with a voltage applied to thepixel Pix, and is emitted as radiant light 68. A display apparatus 1according to a first embodiment can perform display using externallight, and thus can reduce the output of a light-emitting device.

In a state in which external light is incident on the display panel 2,when a voltage applied to the pixel electrode illustrated in FIG. 13increases in the order of the voltage V1, the voltage V2, and thevoltage V3 applied to the pixel electrode, a radiance gradation valueaccording to the external light increases in the order of the voltageV1, the voltage V2, and the voltage V3 applied to the pixel electrodealong a second characteristic graph Tel. In a state in which externallight is incident on the display panel 2, a total sum of a radiancegradation value according to the light source light and a radiancegradation value according to the external light is the gradation valueof the light amount of the radiant light. In other words, in a state inwhich external light is incident on the display panel 2, radiancegradation values with respect to the voltage V1, the voltage V2, and thevoltage V3 applied to the pixel electrode are along a fourthcharacteristic graph Tsum.

For example, the first characteristic graph Tsc indicates that aradiance gradation value according to the light source light when thevoltage V2 is applied to the pixel electrode is smaller than “255”,which is the maximum value of the 8-bit gradation. On the other hand,the fourth characteristic graph Tsum indicates that a radiance gradationvalue corresponding to the voltage V2 applied to the pixel electrodeexceeds “255”. In this way, the gradation value of the light amount ofthe radiant light is larger than the radiance gradation value accordingto the light source light. For this reason, an unintended color, whichis different from a color of each pixel required to display an image inaccordance with an image input signal VS, may be displayed on thedisplay panel 2.

In order to prevent a decrease in recognizability due to the colorshift, the amount of light emitted by the light-emitting device 31 maybe increased. However, this increase in amount of light emitted by thelight-emitting device 31 may increase power consumption of the displayapparatus 1.

Further, in a state in which external light is incident on the displaypanel 2, the light source light L and the external light are scattered,and the radiant light 68 can be visually recognized from the outside ofthe display panel 2. As a result, an image displayed on the displaypanel 2 is brighter than an image in accordance with the image inputsignal VS, which makes it hard for the background to be visuallyrecognized. Furthermore, in the image displayed on the display panel 2,there may be an increased number of the pixels Pix with the radiancegradation values exceeding “255”, so that a chunk of a high-luminanceimage may tend to be displayed, which may be visually recognized asluminance unevenness. In addition, in a state in which external light isincident on the display panel 2, recognizability of an image having asmall luminance difference between the pixels Pix may be decreased.

In order to solve the above mentioned problem, a storage 413 storesinformation of the first characteristic graph Tsc and information of thesecond characteristic graph Tel as lookup tables, according to the firstembodiment. An external light analyzer 412 calculates the secondcharacteristic graph Tel according to a signal ELV of external lightintensity information supplied from an external light setting device 61described above, and generates an adjustment signal LAS based on thissecond characteristic graph Tel. A signal adjuster 414 calculates aradiance gradation value for each of the predetermined voltages appliedto the pixel electrodes and generates a third characteristic graph Tconby subtracting the radiance gradation value of the second characteristicgraph Tel from the radiance gradation value of the first characteristicgraph Tsc. The signal adjuster 414 generates a light source controlsignal LCSA for decreasing the light emission amount of thelight-emitting device 31 such that the radiance gradation value for eachof the predetermined voltages applied to the pixel electrode is alongthe third characteristic graph Tcon.

A light source controller 32 drives the light-emitting device 31 inaccordance with the light source control signal LCSA. As a result, eachradiance gradation value according to the light source light for each ofthe voltage V1, the voltage V2, and the voltage V3 is along the thirdcharacteristic graph Tcon, as illustrated in FIG. 13. In a state inwhich external light is incident on the display panel 2, a total sum ofthe radiance gradation value according to the light source light and theradiance gradation value according to the external light is along thefirst characteristic graph Tsc.

The present embodiment allows a color of each pixel required fordisplaying an image in accordance with the image input signal VS to beeasily displayed, even in a case where external light is incident on thedisplay panel 2 according to the configurational embodiment. For thisreason, the present embodiment can prevent a decrease in recognizabilityof the display panel 2, without increasing the amount of light emittedby the light-emitting device 31. Further, decreasing the amount of lightemitted by the light-emitting device 31 can reduce power consumption ofthe display apparatus 1.

Furthermore, the present embodiment decreases a luminance differencebetween an image displayed on the display panel 2 and an image inaccordance with the image input signal VS, thereby improving a luminancebalance between the image and the background. As a result, the presentembodiment improves the recognizability of the image displayed on thedisplay panel 2. The present embodiment reduces the number of pixels Pixhaving radiance gradation values exceeding “255” in an image displayedon the display panel 2, so that a chunk of a high-luminance image ishardly displayed, thereby suppressing luminance unevenness. Furthermore,the present embodiment also allows an image having a small luminancedifference between pixels Pix to be visually recognized with ease in astate in which external light is incident on the display panel 2,thereby improving the recognizability of the image displayed on thedisplay panel 2.

A display controller 5 generates the light source control signal LCSAfrom a light source control signal LCS in accordance with the adjustmentsignal LAS. The present embodiment thus decreases the amount of lightemitted by the light-emitting device 31 according to the signal ELV ofthe external light intensity information. In this way, the displaycontroller 5 performs control so as to reduce the power consumption ofthe light-emitting device 31 according to the signal ELV of the externallight intensity information supplied from the external light settingdevice 61. The display apparatus 1 can thus reduce its powerconsumption.

Second Embodiment

FIG. 14 is a diagram for explaining a relation between a distance from alight-emitting device and radiance in a state in which no external lightis incident on a display panel. FIG. 15 is a diagram for explaining arelation between a distance from the light-emitting device and radiancein a state in which external light is incident on the display panel. Thesame configuration elements as those described in the configurationalembodiment are denoted with the same reference signs, and overlappingdescription is omitted.

In FIGS. 14 and 15, pixels Pix1, Pix2, Pix3, Pix4, Pix5, Pix6, . . . ,Pixn are arranged in an X direction. Light source light L entering froma light-emitting device 31 travels through the pixel Pix1 toward Pixn.

As illustrated in FIG. 14, in a state in which no external light isincident on a display panel 2, when no voltage is applied to any ofpixel electrodes of the pixels Pix1, Pix2, Pix3, Pix4, Pix5, Pix6, . . ., Pixn, a graph C11 represents a relation between a distance from thelight-emitting device 31 to each pixel Pix in a Y direction, andluminance in each pixel Pix. In a state in which no external light isincident on the display panel 2, when a voltage is applied only to thepixel electrode of the pixel Pix4, a graph C12 represents a relationbetween a distance from the light-emitting device 31 to each pixel Pixin the Y direction, and luminance in each pixel Pix. Furthermore, in astate in which no external light is incident on the display panel 2,when a voltage is applied only to the pixel electrodes of the pixel Pix4and the pixel Pix5, a graph C13 represents a relation between a distancefrom the light-emitting device 31 to each pixel Pix in the Y direction,and luminance in each pixel Pix.

As illustrated in FIG. 14, when a voltage is applied to the pixelelectrode of the pixel Pix4, light source light L propagating throughthe inside of a first light-transmissive substrate 10 and that of asecond light-transmissive substrate 20 is scattered in the pixel Pix4,and the luminance of the light source light L decreases by ΔSC4.Further, when a voltage is applied to the pixel electrode of the pixelPix5, the light source light L that has propagated through the inside ofthe first light-transmissive substrate 10 and that of the secondlight-transmissive substrate 20 is scattered in the pixel Pix5 havingliquid crystal in a scattering state, and the luminance of the lightsource light L decreases by ΔSC5.

As illustrated in FIG. 15, in a state in which no external light isincident on the display panel 2, when no voltage is applied to any ofpixel electrodes of the pixels Pix1, Pix2, Pix3, Pix4, Pix5, Pix6, . . ., Pixn, a graph C21 represents a relation between a distance from thelight-emitting device 31 to each pixel Pix in the Y direction, andluminance in each pixel Pix. As illustrated in FIG. 15, in a state inwhich external light 69 is incident on the display panel 2, when avoltage is applied only to the pixel electrode of the pixel Pix4, agraph C22 represents a relation between a distance from thelight-emitting device 31 to each pixel Pix in the Y direction, andluminance in each pixel Pix. Furthermore, in the state in which theexternal light 69 is incident on the display panel 2, when a voltage isapplied only to the pixel electrodes of the pixel Pix4 and the pixelPix5, a graph C23 represents a relation between a distance from thelight-emitting device 31 to each pixel Pix in the Y direction, andluminance in each pixel Pix.

As illustrated in FIG. 15, in a case where the external light 69 isincident on the display panel 2, the luminance in the pixel Pixincreases by luminance ΔLu. For this reason, the luminance in the pixelPix4 becomes luminance VD4. The light source light L and the externallight 69 are scattered in the pixel Pix4, and the luminance VD4 of thepixel Pix4 decreases by ΔSC4. As a result, an apparent decrease of theluminance in the pixel Pix4 is merely ΔSC41. As a result, the amount ofthe light source light L incident on the pixel Pix5, which is locatedfarther from the light-emitting device 31 than the pixel Pix4,increases. Similarly, the luminance in the pixel Pix5 increases byluminance ΔLu by the incidence of the external light 69, and thus theluminance in the pixel Pix5 becomes luminance VDS. The light sourcelight L and the external light 69 are scattered in the pixel Pix5, andthe luminance VD5 in the pixel Pix5 decreases by ΔSC5. As a result, anapparent decrease of the luminance in the pixel Pix5 is merely ΔSC51.

Since the light source light L propagates through the inside of thefirst light-transmissive substrate 10 and that of the secondlight-transmissive substrates 20, the farther the distance from thelight-emitting device 31 is, the greater the amount of attenuation ofthe light source light L is, as indicated by the graph C11 in FIG. 14and the graph C21 in FIG. 15. As illustrated in FIG. 6, the externallight 69 in the equivalent amount is incident on a region P2 locatedclose to the second side surface 20D and a region P1 located close tothe first side surface 20C. Thus, even if the light source light L isattenuated in the region P2 located farther from the light-emittingdevice 31, the luminance in the pixel Pix increases by the luminanceΔLu, thereby suppressing luminance unevenness within the plane of thedisplay panel 2, and improving luminance evenness within the plane ofthe display panel 2.

As described above, in a case where the external light 69 is incident onthe display panel 2, the luminance in the pixel Pix illustrated in FIG.15 increases by luminance ΔLu. For this reason, even if the output ofthe light-emitting device 31 is decreased by the luminance ΔLu, adisplay apparatus 1 of the second embodiment can acquire the luminancein the pixel Pix in the equivalent amount to the luminance without theexternal light 69. Thus, the display controller 5 generates a lightsource control signal LCSA from a light source control signal LCS inaccordance with an adjustment signal LAS. Accordingly, the light amountof the light-emitting device 31 is decreased according to a signal ELVof external light intensity information. In this way, the displayapparatus 1 according to the second embodiment can perform display usingthe external light, and thus can reduce its power consumption bydecreasing the output of the light-emitting device 31 by the luminanceΔLu.

Third Embodiment

FIG. 16 is a diagram for explaining a lower limit value of a pixelvoltage. The same configuration elements as those described in theconfigurational embodiment are denoted with the same reference signs,and overlapping description is omitted. In a region P1 located close toa light-emitting device 31 illustrated in FIG. 6, a sum of a colorgradation value of a white component generated by mixing a first color,a second color, and a third color, and a color gradation value ofexternal light 69 exceeds the maximum gradation value, and thus an imagedisplayed on a display panel 2 tends to be whitened.

Thus, a display apparatus of a third embodiment performs control so asto change a voltage applied to a pixel electrode of each pixel Pix inaccordance with an signal ELV of external light intensity information,instead of changing the light amount of a light-emitting device 31.

According to the third embodiment, a storage 413 stores, as lookuptables, the information of a first characteristic graph Tsc illustratedin FIG. 13 and the information of a second characteristic graph Telillustrated in FIG. 13. An external light analyzer 412 calculates thesecond characteristic graph Tel in accordance with the signal ELV of theexternal light intensity information supplied from an external lightsetting device 61, and generates an adjustment signal LAS based on thissecond characteristic graph Tel. A signal adjuster 414 calculates afourth characteristic graph Tsum by adding a radiance gradation value ofthe first characteristic graph Tsc and a gradation value of the secondcharacteristic graph Tel for each of predetermined voltages applied to apixel electrode.

The signal adjuster 414 calculates a voltage V2 applied to the pixelelectrode such that the radiance gradation value is “255” in the fourthcharacteristic graph Tsum, which is the maximum value of 8-bitgradation. The signal adjuster 414 calculates a voltage V3 applied tothe pixel electrode such that the radiance gradation value is “255” inthe first characteristic graph Tsc, which is the maximum value of 8-bitgradation.

The signal adjuster 414 illustrated in FIG. 2 generates an image controlsignal VCSA such that a relation between the voltage applied to thepixel electrode and the radiance gradation value along the firstcharacteristic graph Tsc included in an image control signal VCS becomesa relation between the voltage applied to the pixel electrode and theradiance gradation value along the fourth characteristic graph Tsum.Accordingly, the voltage applied to the pixel electrode of each pixelPix is changed to be a voltage obtained by multiplying the voltage byV2/V3. The voltage applied to the pixel electrode corresponding to themaximum value of the 8-bit gradation is adjusted from the voltage V3 tothe voltage V2 applied to the pixel electrode in FIG. 13. As a result, adisplay controller 5 decreases the voltage applied to the pixelelectrode, which is set based on an image input signal VS, in accordancewith the signal ELV of the external light intensity information. In thisway, the display controller 5 performs control so as to reduce the powerconsumption of the display panel 2 according to the signal ELV of theexternal light intensity information. As a result, the display apparatus1 can thus reduce its power consumption.

As illustrated in FIG. 16, the first characteristic graph Tsc can berepresented by the following Equation (1).Ty=α×Vx+b  (1)

In the Equation (1), α and b are determined according to thecharacteristics of a liquid crystal material, a first light-transmissivesubstrate 10, and a second light-transmissive substrate 20, for example.

The second characteristic graph Tel can be represented by the followingEquation (2).Ty=β×Vx+d  (2)

In the Equation (2), μ and d are determined according to thecharacteristics of the liquid crystal material, the firstlight-transmissive substrate 10, and the second light-transmissivesubstrate 20, for example, as well as the characteristics of externallight. The storage 413 illustrated in FIG. 2 stores the values of μ andd according to the signal ELV of the external light intensityinformation as a lookup table. The storage 413 may store the values of μand d according to the signal ELV of the external light intensityinformation as a function or a database instead of the lookup table. Inaddition, μ may take discrete values such as 1, 2, 3, . . . , p orcontinuous values.

As described above, the display controller 5 changes the voltage appliedto the pixel electrode, which is set based on the image input signal VS,to be a voltage obtained by multiplying the voltage by V2/V3, anddecreases the voltage in accordance with the signal ELV of the externallight intensity information. In this way, the display controller 5performs control so as to reduce the power consumption of the drivecircuit 4 according to the signal ELV of the external light intensityinformation.

As illustrated in FIG. 16, when a voltage applied to the pixel electrodebecomes a rise application voltage Vxth or higher, the radiancegradation value starts to increase by the external light 69. In a casewhere the voltage applied to the pixel electrode is lower than the riseapplication voltage Vxth, the influence of the external light 69 on thedisplay panel 2 is small, and thus the display controller 5 does notneed to perform control.

As illustrated in FIG. 16, in a case where the radiance gradation valueaccording to the external light 69 is smaller than the absolute value ofd described above in accordance with the signal ELV of the externallight intensity information supplied from the external light settingdevice 61, the influence of the external light 69 on the display panel 2is small. Thus, the display controller 5 does not need to change thevoltage applied to the pixel electrode, which is set based on the imageinput signal VS, to be a voltage obtained by multiplying the voltage byV2/V3.

The display controller 5 may decrease the amount of light emitted by thelight-emitting device 31 as well as decreasing the voltage applied tothe pixel electrode, which is set based on the image input signal VS.

Fourth Embodiment

FIG. 17 is an explanatory diagram illustrating an example of a colorgradation value of one pixel of an image in accordance with an imageinput signal. FIG. 18 is an explanatory diagram illustrating an exampleof a color gradation value of one pixel of an adjusted image accordingto the configurational embodiment. The same configuration elements asthose described in the configurational embodiment are denoted with thesame reference signs, and overlapping description is omitted.

Changing a voltage applied to a pixel electrode, which is set based onan image input signal VS, changes color gradation values of a firstcolor (R), a second color (G), and a third color (B) of each pixel inaccordance with the image input signal VS. The first color (R), thesecond color (G), the third color (B) respectively correspond to a redcomponent, a green component, and a blue component. A white componentgenerated by mixing the first color (R), the second color (G), and thethird color (B) will be referred to as a fourth color in the presentdisclosure.

As illustrated in FIG. 17, a color gradation value VR1 of the firstcolor is “255”, a color gradation value VG1 of the second color is“200”, and a color gradation value VB1 of the third color is “100”.External light 69 brightens a display panel 2 similarly to the fourthcolor. A color gradation value ΔEW1 of the external light 69 acquiredfrom a signal ELV of external light intensity information, for example,is “166.5”. The display panel 2 is driven by the field sequentialmethod, the color gradation value ΔEW1 of the external light is proratedaccording to the respective magnitudes of the color gradation value VR1of the first color, the color gradation value VG1 of the second color,and the color gradation value VB1 of the third color so as to obtainexternal light color gradation values Er1, Eg1, and Eb1. The colorgradation value ΔVW1 of the white component Wrgb1 generated by mixingthe first color, the second color, and the third color is “100”. A sumof the color gradation value ΔVW1 and the color gradation value ΔEW1exceeds the maximum gradation value “255”, which makes it difficult tovisually recognize a gradation difference among the first color, thesecond color, and the third color of the pixel Pix. As a result, thepixel Pix is represented only as the fourth color.

As illustrated in FIG. 18, a signal adjuster 414 generates an imagecontrol signal VCSA from an image control signal VCS in accordance withan adjustment signal LAS, and decreases a voltage applied to the pixelelectrode by 30%, for example. In other words, the voltage ratio (V2/V3)of a voltage V2 to a voltage V3 illustrated in FIG. 13 is 7/10, and adisplay controller 5 performs control to display a pixel Pix with avoltage applied to the pixel electrode, the voltage being obtained bymultiplying an application voltage for the pixel electrode set based onthe image input signal VS by the voltage ratio (V2/V3).

As illustrated in FIG. 18, a color gradation value VR2 of the firstcolor is “163.5”. A color gradation value VG2 of the second color is“125”. A color gradation value VB2 of the third color is “55”. As aresult, a color gradation value ΔEW2 of the external light is decreasedto be “103.5”. The color gradation value ΔEW2 of the external light 69is prorated according to the respective magnitudes of the colorgradation value VR2 of the first color, the color gradation value VG2 ofthe second color, and the color gradation value VB2 of the third colorso as to obtain external light color gradation values Er2, Eg2, and Eb2.The color gradation value ΔVW2 of a white component Wrgb2 generated bymixing the first color, the second color, and the third color is “55”. Asum of the color gradation value ΔVW2 and the color gradation value ΔEW2is “158.5”.

As described above, the image control signal VCSA is generated from theimage control signal VCS in accordance with the adjustment signal LAS.For example, in a case where the color gradation value ΔVW1 of a whitecomponent generated by mixing the first color, the second color, and thethird color, which is set based on the image input signal VS, and thecolor gradation value ΔEW1 of the external light, which is set based onthe signal ELV of the external light intensity information, exceed themaximum gradation value, the display controller 5 decreases a voltageapplied to the pixel electrode according to the signal ELV of theexternal light intensity information. Accordingly, a display apparatus 1can reduce its power consumption. Further, the present embodiment canimprove the luminance according to the color gradation value ΔEW2 of theexternal light. The present embodiment allows a gradation differenceamong the first color, the second color, and the third color to bevisually recognized, thereby improving the recognizability of an image.

The display apparatus 1 according to the configurational embodimentincludes: the first light-transmissive substrate 10; the secondlight-transmissive substrate 20; the liquid crystal layer 50; thelight-emitting device 31; and the display controller 5. The secondlight-transmissive substrate 20 faces the first light-transmissivesubstrate 10. The liquid crystal layer 50 includes polymer dispersedliquid crystal sealed between the first light-transmissive substrate 10and the second light-transmissive substrate 20. The light-emittingdevice 31 faces the first side surface 20C of the secondlight-transmissive substrate 20. The display controller 5 performscontrol so as to reduce its power consumption according to the signalELV of external light intensity information supplied from the externallight setting device 61.

This configuration has no backlight and no reflection plate on the firstprincipal surface 10A side of the first light-transmissive substrate 10or the first principal surface 20A side of the second light-transmissivesubstrate 20. For this reason, the background on the first principalsurface 20A side of the second light-transmissive substrate 20 isvisually recognized from the first principal surface 10A of the firstlight-transmissive substrate 10, or the background on the firstprincipal surface 10A side of the first light-transmissive substrate 10is visually recognized from the first principal surface 20A of thesecond light-transmissive substrate 20.

Further, the display apparatus 1 according to the configurationalembodiment has no polarizing plate on the first principal surface 10Aside of the first light-transmissive substrate 10 or the first principalsurface 20A side of the second light-transmissive substrate 20. For thisreason, in a case where the background on the first principal surface20A side of the second light-transmissive substrate 20 is visuallyrecognized from the first principal surface 10A of the firstlight-transmissive substrate 10, or the background on the firstprincipal surface 10A side of the first light-transmissive substrate 10is visually recognized from the first principal surface 20A of thesecond light-transmissive substrate 20, the configuration realizes hightransmittance, thereby allowing the background to be visually recognizedwith clarity.

Then, the display controller 5 performs control so as to reduce thepower consumption of the light-emitting device 31 in accordance with thesignal ELV of the external light intensity information supplied from theexternal light setting device 61. Accordingly, in a state in whichexternal light is incident on the display panel 2, the configuration canimprove the recognizability of an image displayed on the display panel2.

The display apparatus 1 includes the pixel electrode 16 serving as afirst electrode and the common electrode 22 serving as a secondelectrode with the liquid crystal layer 50 interposed therebetween. Thedisplay controller 5 decreases a voltage applied to the pixel electrode16, which is set based on the image input signal VS, in accordance withthe signal ELV of the external light intensity information. In this way,the display controller 5 performs control so as to reduce the powerconsumption of the display panel 2 in accordance with the signal ELV ofthe external light intensity information supplied from the externallight setting device 61. Accordingly, in a state in which external lightis incident on the display panel 2, the configuration can improve therecognizability of an image displayed on the display panel 2.

First Modification

FIG. 19 is a plan view illustrating the plane of a display apparatusaccording to a first modification of the configurational embodiment.FIG. 20 is a cross-sectional view taken along line XX-XX illustrated inFIG. 19. The same configuration elements as those described in theconfigurational embodiment are denoted with the same reference signs,and overlapping description is omitted. A cross-section taken along lineV-V illustrated in FIG. 19 is the same as that of the display apparatusaccording to the configurational embodiment illustrated in FIG. 5, andoverlapping description is omitted.

As illustrated in FIGS. 19 and 20, a light-emitting device 31 faces afourth side surface 20F of a second light-transmissive substrate 20. Asillustrated in FIG. 20, the light-emitting device 31 emits light sourcelight L to the fourth side surface 20F of the second light-transmissivesubstrate 20. The fourth side surface 20F of the secondlight-transmissive substrate 20 facing the light-emitting device 31serves as a light incident surface. A gap G is provided between thelight-emitting device 31 and the light incident surface. The gap Gserves as an air layer.

As illustrated in FIG. 20, the light source light L emitted from thelight-emitting device 31 propagates in a direction away from the fourthside surface 20F while being reflected at a first principal surface 10Aof a first light-transmissive substrate 10 and a first principal surface20A of the second light-transmissive substrate 20.

The display apparatus 1 according to the first modification of theconfigurational embodiment includes the first light-transmissivesubstrate 10, the second light-transmissive substrate 20, a liquidcrystal layer 50, and light-emitting devices 31. The two light-emittingdevices 31 respectively face a first side surface 20C and the fourthside surface 20F of the second light-transmissive substrate 20. Theconfiguration increases the amounts of the light emitted from the twolight-emitting devices 31 and propagating through a display panel 2,thereby improving uniformity of the light propagating through thedisplay panel 2.

The display apparatus 1 according to the first modification of theconfigurational embodiment has no backlight and no reflection plate onthe first principal surface 10A side of the first light-transmissivesubstrate 10 or the first principal surface 20A side of the secondlight-transmissive substrate 20, similarly to the configurationalembodiment. This configuration allows a background on the firstprincipal surface 20A side of the second light-transmissive substrate 20to be visually recognized from the first principal surface 10A of thefirst light-transmissive substrate 10, or a background on the firstprincipal surface 10A side of the first light-transmissive substrate 10to be visually recognized from the first principal surface 20A of thesecond light-transmissive substrate 20. The display controller 5 thenperforms control so as to reduce the power consumption of thelight-emitting device 31 in accordance with a signal ELV of externallight intensity information supplied from an external light settingdevice 61. Alternatively, the display controller 5 performs control soas to reduce the power consumption of the display panel 2 in accordancewith the signal ELV of the external light intensity information suppliedfrom the external light setting device 61.

Second Modification

FIG. 21 is a plan view illustrating the plane of a display apparatusaccording to a second modification of the configurational embodiment.FIG. 22 is a cross-sectional view taken along line XXII-XXII illustratedin FIG. 21. FIG. 23 is a cross-sectional view taken along lineXXIII-XXIII illustrated in FIG. 21. The same configuration elements asthose described in the configurational embodiment and the modificationthereof are denoted with the same reference signs, and overlappingdescription is omitted.

As illustrated in FIGS. 21 and 22, a light-emitting device 31 faces asecond side surface 20D of a second light-transmissive substrate 20. Asillustrated in FIG. 22, the light-emitting device 31 emits light sourcelight L to the second side surface 20D of the second light-transmissivesubstrate 20. The second side surface 20D, which faces thelight-emitting device 31, of the second light-transmissive substrate 20serves as a light incident surface. A gap G is provided between thelight-emitting device 31 and the light incident surface. The gap Gserves as an air layer.

As illustrated in FIG. 22, the light source light L emitted from thelight-emitting device 31 propagates in a direction away from the secondside surface 20D while being reflected at a first principal surface 10Aof a first light-transmissive substrate 10 and a first principal surface20A of the second light-transmissive substrate 20.

As illustrated in FIGS. 21 and 23, another light-emitting device 31faces a third side surface 20E of the second light-transmissivesubstrate 20. As illustrated in FIG. 23, the light-emitting device 31emits light source light L to the third side surface 20E of the secondlight-transmissive substrate 20. The third side surface 20E, which facesthe light-emitting device 31, of the second light-transmissive substrate20 serves as a light incident surface. A gap G is provided between thelight-emitting device 31 and the light incident surface. The gap Gserves as an air layer.

As illustrated in FIG. 23, the light source light L emitted from thelight-emitting device 31 propagates in a direction away from the thirdside surface 20E while being reflected at the first principal surface10A of the first light-transmissive substrate 10 and the first principalsurface 20A of the second light-transmissive substrate 20.

The display apparatus 1 according to the second modification of theconfigurational embodiment includes the first light-transmissivesubstrate 10, the second light-transmissive substrate 20, a liquidcrystal layer 50, and the light-emitting devices 31. The twolight-emitting devices 31 respectively face the second side surface 20Dand the third side surface 20E of the second light-transmissivesubstrate 20. The configuration increases the amounts of the lightemitted from the two light-emitting devices 31 and propagating through adisplay panel 2, thereby improving uniformity of the light propagatingthrough the display panel 2.

The display apparatus 1 according to the second modification of theconfigurational embodiment has no backlight and no reflection plate onthe first principal surface 10A side of the first light-transmissivesubstrate 10 or the first principal surface 20A side of the secondlight-transmissive substrate 20, similarly to the configurationalembodiment. This configuration allows a background on the firstprincipal surface 20A side of the second light-transmissive substrate 20to be visually recognized from the first principal surface 10A of thefirst light-transmissive substrate 10, or a background on the firstprincipal surface 10A side of the first light-transmissive substrate 10to be visually recognized from the first principal surface 20A of thesecond light-transmissive substrate 20. A display controller 5 performscontrol so as to reduce the power consumption of the light-emittingdevices 31 in accordance with a signal ELV of external light intensityinformation supplied from an external light setting device 61.Alternatively, the display controller 5 performs control so as to reducethe power consumption of the display panel 2 in accordance with thesignal ELV of the external light intensity information supplied from theexternal light setting device 61.

Preferred embodiments of the present disclosure have been described.However, the present disclosure is not limited by these embodiments. Thecontent disclosed in the embodiments is merely an example, and variousmodifications can be made without departing from the gist of the presentdisclosure. Appropriate modifications made without departing from thegist of the present disclosure obviously belong to the technical scopeof the present disclosure. All the technologies that can beappropriately designed, modified, and implemented by a person skilled inthe art on the basis of the above-described disclosure belong to thetechnical scope of the present disclosure as long as the technologiesinclude the gist of the present disclosure.

For example, the display panel 2 may be a passive matrix panel without aswitching element. The passive matrix panel includes, in plan view, afirst electrode extending in the X direction, a second electrodeextending in the Y direction, and wiring electrically coupled to thefirst electrode or the second electrode. The first electrode, the secondelectrode, and the wiring are formed of, for example, ITO. For example,the first light-transmissive substrate 10 including the above-describedfirst electrode and the second light-transmissive substrate 20 includingthe second electrode face each other with the liquid crystal layer 50interposed therebetween.

The example in which the first orientation film 55 and the secondorientation film 56 are the vertical orientation films has beendescribed. However, the first orientation film 55 and the secondorientation film 56 may be horizontal orientation films. The firstorientation film 55 and the second orientation film 56 only need to havea function to orient the monomers in a predetermined direction inpolymerizing the monomers. This allows the monomers to become polymersoriented in the predetermined direction. When the first orientation film55 and the second orientation film 56 are the horizontal orientationfilms, the direction of the optical axis Ax1 of the bulk 51 and thedirection of the optical axis Ax2 of the fine particle 52 are the same,and are perpendicular to the Z direction, in a state in which no voltageis applied between the pixel electrode 16 and the common electrode 22.The direction perpendicular to the Z direction corresponds to the Xdirection or the Y direction along a side of the firstlight-transmissive substrate 10 in plan view.

The embodiments and the modifications include the following aspects.

(1) A display apparatus comprising:

-   -   a first light-transmissive substrate;    -   a second light-transmissive substrate facing the first        light-transmissive substrate;    -   a liquid crystal layer sealed between the first        light-transmissive substrate and the second light-transmissive        substrate, and including polymer dispersed liquid crystal;    -   at least one light-emitting device facing at least one of a side        surface of the first light-transmissive substrate or a side        surface of the second light-transmissive substrate; and    -   a display controller configured to perform control so as to        reduce power consumption based on a signal, the signal being in        accordance with a signal of external light intensity information        supplied from an external light setting device.        (2) The display apparatus according to (1), wherein    -   the first light-transmissive substrate includes a first        principal surface and a second principal surface that is a plane        parallel to the first principal surface,    -   the second light-transmissive substrate includes a first        principal surface and a second principal surface that is a plane        parallel to the first principal surface, and    -   when the liquid crystal layer is in a non-scattering state, a        background on the first principal surface side of the second        light-transmissive substrate is visually recognized from the        first principal surface of the first light-transmissive        substrate, or a background on the first principal surface side        of the first light-transmissive substrate is visually recognized        from the first principal surface of the second        light-transmissive substrate.        (3) The display apparatus according to (1) or (2), wherein the        display controller is configured to decrease an amount of light        emitted from the at least one light-emitting device in        accordance with the signal of the external light intensity        information.        (4) The display apparatus according to any one of (1) to (3),        further comprising a first electrode and a second electrode with        the liquid crystal layer interposed therebetween,    -   wherein the display controller is configured to set a voltage        applied to the first electrode in accordance with an image input        signal, and decrease the voltage applied to the first electrode        in accordance with the signal of the external light intensity        information.        (5) The display apparatus according to (4), wherein,    -   a first maximum voltage applied to the first electrode is a        voltage by which a radiance gradation value takes a maximum        value in a state in which there is external light, in accordance        with the signal of the external light intensity information,    -   a second maximum voltage applied to the first electrode is a        voltage by which a radiance gradation value of the image input        signal takes a maximum value, and    -   the display controller is configured to calculate a voltage        ratio between the first maximum voltage and the second maximum        voltage and multiply the voltage applied to the first electrode,        which is set based on the image input signal, by the voltage        ratio, so as to decrease the voltage applied to the first        electrode.        (6) The display apparatus according to any one of (1) to (4),        further comprising a first electrode and a second electrode with        the liquid crystal layer interposed therebetween,    -   wherein, when a color gradation value of a white component        generated by mixing a first color, a second color, and a third        color set based on an image input signal and a color gradation        value set based on the signal of the external light intensity        information each exceed a maximum gradation value, the display        controller is configured to decrease a voltage applied to the        first electrode, which is set based on the image input signal,        in accordance with the signal of the external light intensity        information.        (7) The display apparatus according to any one of (1) to (6),        wherein the external light setting device is an external light        intensity sensor, and is configured to generate the signal of        the external light intensity information in accordance with        intensity of detected external light.        (8) The display apparatus according to any one of (1) to (6),        wherein the external light setting device is a setting switch        capable of changing a setting value of the external light        intensity information, which is set based on intensity of        external light in advance, and the external light setting device        is configured to generate the signal of the external light        intensity information in accordance with the setting value of        the external light intensity information.

What is claimed is:
 1. A display apparatus comprising: a firstlight-transmissive substrate; a second light-transmissive substratefacing the first light-transmissive substrate; a liquid crystal layersealed between the first light-transmissive substrate and the secondlight-transmissive substrate, and including polymer dispersed liquidcrystal; at least one light-emitting device facing at least one of aside surface of the first light-transmissive substrate or a side surfaceof the second light-transmissive substrate; a display controllerconfigured to perform control so as to reduce power consumption based ona signal, the signal being in accordance with a signal of external lightintensity information supplied from an external light setting device;and a first electrode and a second electrode with the liquid crystallayer interposed therebetween, wherein the display controller isconfigured to set a voltage applied to the first electrode in accordancewith an image input signal, and decrease the voltage applied to thefirst electrode in accordance with the signal of the external lightintensity information, a first maximum voltage applied to the firstelectrode is a voltage by which a radiance gradation value takes amaximum value in a state in which there is external light, in accordancewith the signal of the external light intensity information, a secondmaximum voltage applied to the first electrode is a voltage by which aradiance gradation value of the image input signal takes a maximumvalue, and the display controller is configured to calculate a voltageratio between the first maximum voltage and the second maximum voltageand multiply the voltage applied to the first electrode, which is setbased on the image input signal, by the voltage ratio, so as to decreasethe voltage applied to the first electrode.
 2. The display apparatusaccording to claim 1, wherein the first light-transmissive substrateincludes a first principal surface and a second principal surface thatis a plane parallel to the first principal surface, the secondlight-transmissive substrate includes a first principal surface and asecond principal surface that is a plane parallel to the first principalsurface, and when the liquid crystal layer is in a non-scattering state,a background on the first principal surface side of the secondlight-transmissive substrate is visually recognized from the firstprincipal surface of the first light-transmissive substrate, or abackground on the first principal surface side of the firstlight-transmissive substrate is visually recognized from the firstprincipal surface of the second light-transmissive substrate.
 3. Thedisplay apparatus according to claim 1, wherein the display controlleris configured to decrease an amount of light emitted from the at leastone light-emitting device in accordance with the signal of the externallight intensity information.
 4. The display apparatus according to claim1, wherein the external light setting device is an external lightintensity sensor, and is configured to generate the signal of theexternal light intensity information in accordance with intensity ofdetected external light.
 5. The display apparatus according to claim 1,wherein the external light setting device is a setting switch capable ofchanging a setting value of the external light intensity information,which is set based on intensity of external light in advance, and theexternal light setting device is configured to generate the signal ofthe external light intensity information in accordance with the settingvalue of the external light intensity information.
 6. A displayapparatus comprising: a first light-transmissive substrate; a secondlight-transmissive substrate facing the first light-transmissivesubstrate; a liquid crystal layer sealed between the firstlight-transmissive substrate and the second light-transmissivesubstrate, and including polymer dispersed liquid crystal; at least onelight-emitting device facing at least one of a side surface of the firstlight-transmissive substrate or a side surface of the secondlight-transmissive substrate; a display controller configured to performcontrol so as to reduce power consumption based on a signal, the signalbeing in accordance with a signal of external light intensityinformation supplied from an external light setting device; and a firstelectrode and a second electrode with the liquid crystal layerinterposed therebetween, wherein, when a color gradation value of awhite component generated by mixing a first color, a second color, and athird color set based on an image input signal and a color gradationvalue set based on the signal of the external light intensityinformation each exceed a maximum gradation value, the displaycontroller is configured to decrease a voltage applied to the firstelectrode, which is set based on the image input signal, in accordancewith the signal of the external light intensity information.
 7. Thedisplay apparatus according to claim 6, wherein the external lightsetting device is an external light intensity sensor, and is configuredto generate the signal of the external light intensity information inaccordance with intensity of detected external light.
 8. The displayapparatus according to claim 6, wherein the external light settingdevice is a setting switch capable of changing a setting value of theexternal light intensity information, which is set based on intensity ofexternal light in advance, and the external light setting device isconfigured to generate the signal of the external light intensityinformation in accordance with the setting value of the external lightintensity information.